DISEASE CHARACTERISTICS: Histologically or cytologically confirmed adenocarcinoma of the prostate Stage IV Evidence of progression despite standard hormonal management including antiandrogen withdrawal, defined as 1 of the following: Development of new metastatic lesions Increase in cancer-related pain A 50% rise in prostate-specific antigen (PSA) levels confirmed by 2 measurements at least 2 weeks apart PSA at least 5 ng/mL Testosterone less than 50 ng/mL